In the rotary drilling of wells, and particularly oil and gas wells, a rotary table having an opening and kelly, which is an elongate member, flat faced in cross section, is slidable through a similarly-shaped kelly bushing secured to the rotary table and is secured to the upper end of the drill string therebelow for rotating the drill string rotary bit at its lower end during drilling. The kelly is used only during the actual drilling, and when not in use is stored in an out of the way position in what is referred to as a "rat hole." In the past, rat holes for storing the kelly have ranged from holes drilled into the ground to casing secured to a structural member of a drilling rig, for example, as illustrated in U.S. Pat. No. 3,371,728.
As the art of rotary drilling has progressed, and particularly in drilling for oil and gas in submerged offshore lands, both from fixed or floating vessels, it is highly desirable that a rat hole assembly be provided which is anchored to the drilling rig at its lower end, which rat hole is movable toward the rotary table for reception of the kelly for storing and moving to an out of the way position so that other operations may be performed without interference with the kelly, yet movable back toward the rotary for withdrawal when rotary drilling operations are to be commenced again, and which rat hole can be readily removed from the structural member when desired, for example, when moving from one location to another.